The invention relates to a method of checking the operability of a cyclically controlled regeneration valve in a tank venting system of a motor vehicle.
German Offenlegungsschrift 4,112,481 discloses a method of this kind, by means of which it is possible to check the operability of the regeneration valve and that of the entire tank venting system. Here, the differential pressure in the tank venting system relative to the ambient pressure is first measured with the regeneration valve open and then with the regeneration valve closed. The change in the differential pressure calculated therefrom is then compared with a threshold value and the tank venting system is considered to be functional if the change in the differential pressure exceeds the threshold value. This method has the disadvantage that it is necessary to close the regeneration valve to check its operability and, as a result, the normal operation of the tank venting system must be interrupted for the duration of the operability check.
It is therefore the object of the invention to provide a method by which the operability of a cyclically controlled regeneration valve in a tank venting system can be checked without interrupting normal operation.